Blast Pocket is a gear perk that lets you carry more grenades, dynamite and pipebombs. It suits players who like solving problems with thrown explosives.
Your carry limit for thrown explosives goes up, so you can keep throwing through a long fight.
Wear one of the gear pieces that carry it: First Blood Fatigues. Each piece only takes one body slot, so plan around the other perks you want.
Worth it if you throw explosives often. If you prefer guns, pick a defense perk for this slot.